Preparation of 1, 5-pentanediols



Patented Mar. 20, 1951 UNITED STATES PAT ENT OFFICE 2,546,019 PREPARATION OF 1,5' PENTANEDIOLS' Curtis W. Smith, Berkeley, Calif., assignor to Shell- Development Company, San FranciscmCalifl', a corporation of Delaware NoDrawing. Application'fictober 25, 194 7 a Serial No. 782,229

12 Claims.-

This invention relates to a-vmethod for the preparation of l,5-diols,-,and more particularly relates to a method for the production of 1,5-

,.diols, by the simultaneous treatment with hytion is amethod to prepare such diols, in particular 1,5-pentanediol, in high yields and with aminimum of manipulative steps.v

An additional object of the invention istoprepare 1,5'-diols from compounds in the dihydropyran series of compounds in high yields and with a maximum of efficiency in operation.

An ancillary object of the invention is a process that may be carried out, as in commercial operation'of' the'process', by one not skilled "in the art,e. g., a chemicallyuntrained operator, with minimum'' danger of unsuccessful outcome arising from lack of precise control by the operator or from lack of chemical'skill on the part of the operator.

A more specific objectof' the invention is an improved process for the preparation of 1,5-

,di'ols, particularly" 1,5-p'entan'ediol, from compounds in the dihydropyran series of compounds.

Other related objects of the invention will become apparent as the invention is more particularly described hereinafter.

It has been proposed (see Bull. soc. chim. ['5] l, 971 (1934)) to prepare 1,5-pentaned-iol by treating dihydropyran-IA.

with N/70 aqueous hydrochloric acid at reflux temperature; and reducing the resultant prodizi-ng, theintermediatev product, and (c) reducing the intermediate product. Furthermore, the

. rather expensive amalgam.

An improvement on the foregoing known process has been proposed (see J. Am. Chem. Soc., 68,.1646 (1946)) which comprises hydrolyzing the dihydropyran,.carefully neutralizing the resultant mixture, isolatingthe intermediate product that was formed by hydrolysis, and hydrogenating the isolated intermediate productv by treatment with hydrogen gas under a-pressure of 2000zpounds per square inch and at C. in the presence of copper-chromite hydrogenation catalyst. Although va certain improvement, in yield over. thepreviously knownprocess was disclosed, it was-found that attempts to carry out the process without the intermediate isolationof the product of the hydrolysislresulted in a substantial reduction in. the yields that. were. obtained. It also was found that the accuracy with which the acid in thehydrolysis mixture was neutralized prior to distillationof themixturewas an important factor in determining. the yields that were obtained, failure to carefully neutralize the acid leading to substantially reduced yields of the desired 1,5 -pen'tanediol. Therefore,.this latter process, while representing anadvance over the first-mentioned known process, was not entirely satisfactory because (a) it required theseveral steps enumerated'immediately above (b) each additional step would require additional apparatus. and/or additional working time, (c) the process would'require the skillful manipulation of the intermediate mixtures in' order to obtain optimum. yields of the desired product and (at) even under the optimum conditions as disclosed, the yields of the desired product that were obtained were not. as high as couldbe desired While for laboratory purposes a process having these features might not be highly objectionable, such features couldimpair significantly the. usefulness and value of a process for application on a scale of commercial. operations because of the expenseot the equipment and skilled operators time that would be required and because o'fthe' careful control with which the neutralization step of the process would have to be carried out to avoid undesirable reduction in the yield'of'the desired product;

In the attainment of its objects, the present invention has overcome the difficulties that thus are associated with the prior art process and in so doing. hasprovided a process whereby, 11'5- diols may be prepared in a single step from compounds in the dihydropyran series of compounds, without reduced yields compared to the yields that are obtained in a process, such as the above prior art processes, that comprise a plurality of steps. The present process may be executed under conditions which may be maintained within relatively wide limits and without the necessity for precise control or skillful manipulation that are required for the attainment of optimum yields according to the prior art methods. As a consequence, the process of the present invention is better suited to application on a commercial scale than are the mentioned prior art processes. Furthermore, the process of the invention has provided an improvement over the prior art methods of preparing 1,5-diols from compounds in that there may be obtained, despite the single step character of the process, yields of the desired product substantially greater than the yields that heretofore have been attained.

Broadly stated, the process of the present invention comprises hydrolyzing in the presence of a hydrogenation catalyst and of hydrogen under conditions which favor hydrogenation reaction, a substituted 3,4-dihydro-L2-pyran containing an organic substituent group attached by a hydrolyzable bond to the carbon atom in the No. 2 position of the dihydropyran ring through a divalent atom of a non-metallic element of group VI of the periodic table of the elements. It has been discovered in accordance with the present invention that by subjecting to simultaneous hydrolysis and hydrogenation derivatives oi 3,4-dihydro-1,2-pyran which contain an organic substituent group that may be removed, or split-off, by hydrolysis attached to the carbon atom in the No. 2 position of the dihydropyran ring through a divalent atom of a non-metallic element of group VI of the periodic table of the elements, there may be obtained 1,5-diols in yie ds that are at least equal to the yields that the obtained by successively hydroiyzing the same derivative of dihydropyran, isolating the hydrolysis products, and hydrogenating the isolated products of the hydrolysis. The results that are thus provided by the invention are critically dependent upon the presence in the 2-position of the dihydropyran ring of such a substituent group that may be removed, or split-off, by hydrolysis, since attempts to simultaneously hydrolyze and hydrogenate 3,4-dihydro-1,2-pyran or a derivative thereof which does not contain at the No. 2 position a substituent group of the above defined character, lead to yields substantially below the yields that are obtained by successively carrying out the enumerated steps.

If, in the following formulas, R represents the 2-(3,4-dihydro-L2-pyranyl) group or a substituted 2-(3,4-dihydro-L2-pyranyl) group, the derivatives of dihydropyran which preferably may be employed in the execution of the process of the present invention may be represented by the structural formulas in which the free valencies at the O and S atoms, respectively, are satisfied by organic groups which preferably are bonded to the indicated free valencies at an atom of carbon. In most cases the desired 1,5-diol is derived solely from the carbon atoms of the 2-(3,4-dihydro-1,2- pyranyl) group or the substituted 2-(3,4-dihydro-1,2-pyranyl) group represented by R. The carbon atom or atoms of the organic group that is attached to the free valency of the S or the O atom in the above formulas ordinarily do not form a part of the desired product. (The exception to the general rules arises in certain cases in which an additional amount of the diol may be derived from the said organic group. It will be apparent, therefore, that the exception does not limit the following sentence, but, instead, is an exception only to the generalities described in the two sentences immediately preceding). From the standpoint of operability in the presence of the invention, the substituted dihydropyran therefore may be one which contains any of a wide variety of substituent groups attached by a hydrolyzable bond to the carbon atom in position No. 2 of the dihydropyran ring through a divalent atom of oxygen or sulfur. Illustrative of the substituted 3,4-dihydro-l,2- pyrans which may be employed in the execution of the process of the invention are included, among others, those which have the following exemplary groups attached to the carbon atom in the No. 2 position of the dihydropyran ring: OR, SR', -OOCR,O--SCR, -SOC-R', S-SCR', etc., in which R represents an unsubstituted or a substituted hydrocarbon group.

Additional substituent groups, such as one or more hydrocarbon groups, may be attached to carbon atoms in the dihydropyran ring, such hydrocarbon groups, if present, preferably being non-reactive to hydrogen under the conditions under which the process is executed, e. g., hydrocarbon groups containing only saturated or aromatic carbon-to-carbo-n bonds, such as alkyl, cycloalkyl, aryl, alkaryl, aralkyl, and like groups. A preferred group of derivatives of 3,4-dihydro1,2-pyran wh.ch may be employed in the execution of the process of the present invention comprises those derivatives which have structures that may be represented by the formula r pounds corresponding in structure to the above formula may be employed to produce with particular and outstanding efiicacy and in particularly high yields, 1,5-diols which are desired in accordance with the invention. The over-all reaction which is caused to take place by the process of the invention may be exemplified, but not limited in the scope of its applicability, by the preparation of 1,5-pentanediol from a derivative of 3,4-dihydro-l,2-pyran having the above structure when R signifies the unsubstituted 243,4- dihydro-1,2-pyranyl) group, as follows:

It will be noted that in this equation the group represented by R does not form a part of the desired product. The specific identity of the ectopic d, in fact, the hydrocarbon group theprocess'a v I v y R" "maybe almost any hydrocarrepresented substituted or substituted. -It is preferredthat the group R "be relatively non-reactive with hydroge'n,'-"i. -e., a saturatedor an aromatic group seen-as an *alkyl, arylyaralkyl, -alkaryl,:cycloalkyl, or like*grup, since unnecessarysaturation or unsaturated carbonto-carbonlinkages in the group R otherwise may occur during the exe- Icution :or the process. it is particularly :desirable that th'e group R be such that the hydrox- OI-fis :mis'ciblewith water,:e. 'g., a' lower 'alkyl group, although theinvention is not tobe-construediasithuslimitediin-its1moreigeneric aspects. Representative hydrocarbon groups which. may be represented by :R' include, *i or ex :ample, :phenyl, tolyl,xylylyphenethyl, cyclohexyl, cylopen'tyl, .methylcyclopentyl, ethylcyclohexyl, .heptyl, octyl, decyl, stearyl, phenylhexyl, tolylbutyl, and homologous -.and1ana1og,ous groups; less desirably groups containing oneor more nonaromatic unsaturated carbon-.to-carbon bonds, such as'vinyl, allyl, methallyl, cyclohexenyl, crotyl, *cinnamyl,- -and the like, and most desirably the lower alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and their branched chain analogs. Apreferred-groupofderivatives of dihydropyran which may be employed in the execution of the process of theinvention has the iormula in whichiR' has its "abovesignifica'nce and each R"represents a hydrogen atom or a hydrocarbon group, preferably ahydrocarbon group which is relatively resistant to hydrogenation, such as an alkyljaryl, alkaryl, 'aralkyl, cycloalkyl group, orthe like. The "completely aliphatic 1,5-diols, ifel, he -1,5-alkanedio1s', are particularly valuable products-for certain applications in the arts. 'For'the preparation oi'lg 5-alkanediols, we may employ derivatives of 'dihydropyran correspondingto the last-given formula when ach'R 'r'epresen tsa hydrogen atom or an-alkyl group, prefer ably one'cont-a'ining from 1 "to about 'caibon'atoms.

Illustrative derivatives of dihydropyran which "maybe employed in the process 'of'the present invention' 'may 'be illustrated by the following non- Iimiting group of compounds: '2-(3,4-dihydro- 1,-2-pyranyl) methyl ether, -2-'(3,4-dihydro-l,2- "pyranyb ethyl ethei,"2-'(3,4-dihydro 1,2-pyranyl) propyl --ether, 2 (4methyl 3j4-dihydro 1,2-pyr- 'anyl) isopropyl ether, 2- 5-methyl-3A-dihydrol,'2"-pyrany1)-'-butyl ether, 2-(5-'b1ityl-3,4-'dihy- =-d'ro-'1",2pyranyl) 'isobu'tyl ether, 2-(2-methyl- 3, kdihydrO lB pyranyl) isopropyl ether, 1 2- (2,4-

dimethyl 3j le'dihy'dro-1,2-pyranyl) methyl ether, 2- (lcyclchexyl 5' methyl-3,' 4 dihydro- 1,2 -pyranyl ethyl ether, 2-(5-15henyl-3A-dihydro 1,2- pyranyl) isobutyl :ether, 2-(6-methyl-3,4-dihy- ='.di'o-1,2epyranyl) methyl ether,2-'(5-octyl-3,l-di- .hydroeli2epyranyl) propyl ether, 12-(5-phenethtyJ G-methyl 3-,4 dihydro 1,2 pyranyl) pentyl "gather andlanalogous and homologous zcompounds.

11' group, and maybe'sa'turated 'orunsaturated, acyclic-or cyclic, aromatic or non aroma'tic, un-

Aecordin'g -to one embodiment of the invention, th' compo'und RFO-R may he symmetrical,

e., R and R both may represent 2-(3,4-dihydrQ- LZ-pyranyl) groups or substitution products thereof. In this embodiment of the invention, the formation of the by-product alcohol RO'H -is avoided, both of the groups R and-R reacting to form a diol of thedesired type with consequent efiiciency of the process with respecttothe carbon'balance between the organic reactant and the desired product.

Deriva'tives of 3,4-dihydro-1,2-pyran which -may be employed in the process of the invention maybe prepared conveniently and economically according to the method disclosed and claimed in the copending application, Serial No. 751,980, "filed iJune '2, 1947, now Patent No. 2,514,168. According to the method of the-copending application, an alpha,beta-o1efinicaldehyde, such as acrolein or a substituted acrolein containing an alkyl, aryl, alkaryl, or aralkyl groupattached to either orto each of'the alpha and the beta carbon atoms, may be reacted with a vinyl compound GH2=CHOR, in which R has its hereinabove significance, at an elevated temperature under conditions which substantially minimize polymerization of the reactants, to prepare directly and 'in a single step the above derivatives of 3,4-dihydro-1,2-pyran which advantageously may be utilized'in the present process. The method of the-aforesaid copending application may be practiced by heating a mixture of the alpha,beta- .olefinic aldehyde and the said vinyl compound present in about equimolar proportions containing an amount of a polymerization inhibitor, such as hydroquinone, sufiicient' to substantially minimize polymerization, to a temperature of about CQtoabout 225 .C. under an elevated pressure'suffici'ent'to-maintain the reaction mixture in the liquid state. Reaction times of from about 4/2 to about 2 hours may be employed. After the reaction, the desired product formed thereby may bezseparated from thereaction mixture prior to its use-in the presentrprocess, or in some cases :the entire reaction mixture in its crude form may 'be'employed'for the preparation of 1,5-di01s :according'to the process'of thepresent invention.

Ihe iprocess of the present invention 'may be 'carried'out by hydrogenatingin the presence of an. aqueous'mediumand a hydrogenation catalyst under conditions .of elevated temperature and superatmospheric pressures of hydrogen conducive 'to hydrogenation reaction, a derivative of 3,4 dihydroel',2pyranof theherein definedcharacter. .As the hydrogenation catalyst theremay be employed any suitable metal or compound of a metal :of the type well-known and customarily referred toiin the .artas hydrogenation catalysts. It is desirable to employ as the hydrogenation catalysta metal ora compound ofa metal which may be easily and economically prepared, which has :a highvdegreeof activity, and which retains its activity :under the conditions of the process fo-nazlength'of time sufficient to avoid the necessity of :reactivating .or replacing the catalyst at too frequentintervals. Generally speaking, hy- 'drogenation catalysts which'may be employe'd'in .the "execution of the process of the invention inelude the metal hydrogenation catalysts, such as 1%, Pd, Au, Ag, Cu, V, W, Co, Ni, Ru, Rh, Mn, or, M0, in Os,'Pb, and the like and mixtures of the same and compounds and alloys thereof, "particularlyoxides"and sulfides thereof, and like hydrogenation:catalysts. Because of theteas'eand acids, and the like.

economy with which they may be prepared, and

because of their characteristics which render .them particularly suited to the objects of the invention in the way of providing high yields of the desired product and their lack of tendency to promote undesired side reactions, the base metal hydrogenation catalysts, particularly the pyrophoric base metal hydrogenation catalysts such as nickel, cobalt, and iron, are preferred. Be-

cause of its availability and its particular efiicacy when employed in the process of the invention, the well-known nickel hydrogenation catalyst customarily referred to in the art as Raney nickel hydrogenation catalyst is a preferred catalyst. The hydrogenation catalyst may be employed in a finely divided form and dispersed in and throughout the reaction mixture, or it may be employed in a more massive state, either in essentially the pure state or supported upon or carried by an inert or catalytically active supporting or carrier material, such as pumice, kieselguhr, diatomaceous earth, clay, alumina, charcoal, carbon, or the like, and the reaction mixture contacted therewith as by flowing the mixture over or through a bed of the catalyst or according to other methods that are known in the art.

If desired the process of the present invention may be executed in the presence of a suitable acid-reacting material which serves to acidify the aqueous medium and thereby increase to a certain extent the reaction rate under the otherwise existing reaction conditions. In large scale applications of the process, it frequently may be advantageous to carry out the process employing a non-alkaline aqueous medium that con- 3 i tains a minimum of added acid-reaction materials, thereby avoiding or minimizing any additional steps that would be required for the purpose of separating the acid catalyst from the reaction mixture as a part of the treatment leading to recovery of the desired product. If an acidic catalyst is employed, any suitable acid-reacting material may be used, such as a strong mineral acid, an acid-reacting salt, or a material which will react under the conditions of the process to form in situ an acid-reacting material. The acid-reacting material must be one that does not adversely affect the hydrogenation catalyst, i. e., it must be non-poisonous to the hydrogenation catalyst. Suitable acid-reacting materials which may be employed to increase the reaction rate include, for example, mineral acids, such as HCl, H2SO4, 1131, HI, H3PO4, H4P2O7, HNOa, I-lzSeOr, H2SO3 and the like; acid-reacting salts, such as NaI-ISOe, NaH2PO4, KH2PO4, ZI1C12, MgClz, ZIISO4, FeCla, A12(SO4)3, and the like. There also may be employed compounds which form mineral acids with water, such as SOzClz, SOCla, N203, PO13, PC15, and the like. As the acidifying agent there also may be employed suitable organic acids, particularly the water-soluble organic acids, such as the lower aliphatic carboxylic acids, halogenated aliphatic carboxylic acids, dibasic carboxylic acids, aromatic acids, and the like. It is not necessary that the acid-reacting catalyst be infinitely soluble in water, since it is necessary only that amounts sufficient to influence the reaction rate be present in the dissolved state. Therefore, organic acids that are less soluble in water, than those just mentioned also may be employed as the acidifying agent if desired, including, for example, aromatic sulfonic acids, higher, less-soluble aliphatic carboxylic acids, dialkyl and alkyl sulfates, alkylated phosphoric Because of their freedom from any tendency to poison the hydrogenation catalysts that may be employed in the execution of the process of the invention, the lower fatty acids, such as the lower fatty acids containing from one to about four carbon atoms are particularly effective for use in the process of the invention. It is desirable, if an acid catalyst is employed, to use one that is easily separated from the reaction mixture after completion of the desired reaction, or, alternatively, one from which the desired product may be easily separated. The volatile organic acids, such as the lower aliphatic monocarboxylic acids are advantageous in this respect because they generally may be conveniently separated from the desired product as by fractional distillation of the reaction mixture. Mineral acids such as sulfuric acid,

hydrochloric acid, or the like, may be removed from the reaction mixture after completion of the reaction by addition of a suitable base or basic salt which forms a water-insoluble of lime or calcium carbonate or of baria, hydrochloric acid may be neutralized by the addition of silver oxide, etc., and the resulting insoluble salt may be removed by filtration or in other ways that will be apparent to those skilled in the art.

The amount of the acidifying agent, if one is employed, may be varied over relatively wide limits. Strong mineral acids and acid-reacting substances of equivalent acidic strength may be employed in amounts of from about 0.00005 to 1 or more acid-equivalents per liter of Water, amounts not over about 0.2 acid-equivalent per liter of water being preferred. Amounts of acetic acid and weak acids of equivalent acidic strength up to about 5% by weight, based on the weight of the water, have been found to provide highly favorable results. More broadly speaking, amounts of the acid-reacting material from 0 up to about 40% by weight of the water that is present may be employed. When the acid catalyst is one that must be removed, as by neutralization, prior to recovery of the desired product, it usually is desirable to employ only small amounts in order to minimize the consumption of acid in the process. Those acids which can be recovered as such from the reaction mixture, 1. e., without neutralization, usually may be employed in somewhat larger amounts without uneconomic consumption of acid. Because of the possibility that the presence of excessive amounts of an acid or acid-reacting material would afiect adversely the activity of the hydrogenation catalyst, it is particularly preferred to employ from about 0% to about 2% by weight of the acidifying agent, based on the weight of the water that is present.

The process of the invention may be executed effectively when water (i. e., distilled or tap water) is employed as the aqueous medium. However, the invention also includes the addition to the aqueous medium of substances which facilitate the reaction as by their physical effect in the reaction mixture. For example, if it is desired to render the derivative of dihydropyran more miscible with the aqueous medium in those instances in which the two are highly immiscible, mutual solvents, such as lower alcohols, heterocyclic oxygen-containing solvents, glycols containing, for example, from 2 to 3 carbon atoms, and the like, may be included in the mixture. Although their presence is not essential to the successful execution of the process of the invention, such additional materials may desirably facilitate the carrying out of the process,. pos- 9;; sibly through their efiectupemthe physical characteristics of the. reaction. mixture.

'lfheamountof the aqueous medium thatis.

mum to the amount of the water that may be. present, althoughfor practical reasonsit. is,de.-. sirableto maintain. the. amount within reasonable In order to avoid excessive dilution. of

limits. the reaction mixture, with consequent reduction in? the. effectiveness of the contact; between the organicreactant and the hydrogenation catalyst, it, is.desirable.to employ not-overabout 100. moles of-lwater per mole of the substituted3A-dihydro- 1,2;pyran, a,.preferred maximum being about 10, mles.of.water permole of substituted 3,4.di-

hydro- 1,2-pyran.

,The. process of the-invention may be executed,

by treating a mixture of the substituted3A-dihydr.o-.-l,2-pyran and theaqueous medium in the presenceof. the hydrogenation catalyst with hydrogen or. a. hydrogen-containing gas at any ele-- vatedtemperature and under superatmospheric pressure ofhydrogenuntil the absorption-of hydrogen is, essentially complete, and recoveringfrom the mixture. the 1,5-diol that. thereby is formed. Broadly speaking, temperatures offrom,

about5'0C. to about 350 C. may be employed... A preferred range of. temperatures comprises temperatures at. which the reaction proceeds at a rate most. suited to practical application of the.

process while avoiding the possibility of excessive. side reactions which could occur atexcessively. elevated temperatures andcomprises temperatures within the range of from about 100 C. to. about 250 C. Hydrogen pressures greater than about 250 pounds per square inchare efiective for accomplishing the objects of the invention. The maximum pressure of hydrogen that may, be-employed is determined largely by the strength of the equipment that is used, and is. not knownto be critical. A convenient maximum pressure, of hydrogenis 10,000 pounds per square inch,. and. aIpreferred range of hydrogen, pressures isfrom about 1000 to about 5000 pounds per square. inch..

The process of the present invention may be executed in any suitable manner and in any suitable. apparatus of the type{that is customarily employed for hydrogenationprocesses. A.meth- 0d of carrying. out the process which has been found to. be advantageous comprises mixing the substituted 3,4-dihydro-L2-pyran with the aqueous medium in a. pressure-resistant vessel equipped with the necessary inlets and outlets, heat ing means, pressure guage thermometer, etc., and desirably. with. means foragitatingthe contents; and subjecting. the mixture. to the action. of hydrogen. gas under the aforesaid conditions.

oft. temperature and pressure in the. presence of the hydrogenation catalyst until absorption of hydrogen is for practicalpurposes complete. Instead of in a bat'chwise method, the. process may. be. carried. out; in an. intermittent or continuous.

manneniallsby-flowing a stream ofamixturecom is desiredasthe; ultimate product ot the-process,

- steps such as those involving. separation of an intermediate reaction: product, or adjustment. or manipulation of an intermediate reaction mixture, being avoided. At the; conclusion of the hydrogenation treatment, the desired product thereforegmay be recovered directly fromthe reactionmixture-in any suitable manner. For.-ex.--.-.

ample, the hydrogenation catalyst, if dispersed in the reaction mixture; may beremoved byfiltration; centrifugation, orby other means which will be apparent. tothose: skilled in theart. If.

anacidifying; agent .is present? and its continued presence during" the recovery treatment; would be objectionable, it-mayberemoved at this time, iltlustrative, suitable methods for itsremoval have. The desired ing beenreferred tohereinbefore; 1,5-diol'1 may be. further purified" in any suitable manner, such as by-evaporation or distillationof they more volatile components of the remainingmixture, by fractionaldistillation, by treatment with selective solvents, by crystallization, or according to other possible methodsv that Wi11Tbe= known to those skilled in'.the art;

The following examples: will illustrate certain of the possible specific embodimentsof the invention. It will be appreciated that the examples are presented for the purpose-of illustrating the inventionandnot t9 unncessarily limit the same as-it'is defined in the appended claims. It also,

Example I One thousand, parts ofv 2.- (3,4 -dihydro -1,2-.; pyranyl) methyl, ether and v 316- parts of. water. were mixed .in, a pressure-resistant reactionvessel suitablefor hydrogenationprocesses. The vessel. was constructedof S..A. E. 41.40 hydrogenation steel and was equipped, with. the customary-there. mometer for. measuring the temperature of the contents, a pressure, gauge, a stirrer, and internally. located heating coils through which. steam could be passed,and.was provided with an inlet for hydrogen, etc. To. themixturethere were added 65 parts of Raney nickel hydrogenation catalyst. The vessel was-closed from the atmosphere and air remaining in the vessel was washed out: with hydrogen gas. Hydrogenunder pressure was introduced into the vessel', and the contents were heatedwithagitation tol50? C.-

under a hydrogen. pressure of 1500 pounds-persquareinch. After four hours, thepressu-r-e was released, and the reaction mixture was taken; from the; reaction vessel and filtered to remove; The .filtrate was tion distilling from 103. o. to 108 0. under a pressure of 1 mm.,Hg-. The above yield figure.-

takes credit for a small amount of a mixture of intermediate products thatwas separated as a forecutduring the. distillation. By. the use of :15 slightly more rigorousgconditigns during, the-hy-l drogenation or by re-passing it through the Example II A mixture of 510 parts of 2-(4-methyl-3A- dihydro-1,2-pyrany1) methyl ether, 250 parts of water, 200 parts of methyl alcohol, and 2 parts of glacial acetic acid was placed in the reaction vessel that was employed in Example I. One hundred parts of Raney nickel hydrogenation catalyst were aded to the mixture. The mixture was subjected to the action of hydrogen, with agitation, at a temperature of 150 C. and a hydrogen pressure of 1300 pounds per square inch for two hours. The mixture then was taken from the reaction vessel and filtered to remove the hydrogenation catalyst. The filtrate was fractionally distilled. After distillation of water and methanol, 3-methyl-15-pentanediol was separated as a fraction distilling from 84 to 95 C. under a pressure of 0.7 mm. Hg in the amount of 320 parts, corresponding to a yield of 71.5% based on the amount of the methvldihydropyranyl methyl ether that was consumed.

Example III A mixture of 560 parts of 2-(5-methyl-3A- dihydro-1.2-pyrany1) n-butvl ether, 500 parts of water, and 2 parts of glacial acetic acid was prepared and placed in the reaction vessel that was used in the foregoing examples. One hundred parts of Raney nickel hydrogenation catalyst were added to the mixture and the mixture was exposed, with agitation, at a temperature of 150 C. for 16 hours to hydrogen gas under a pressure of 1200 pounds per square inch. The mixture then was taken from the reaction vessel, the hydrogenation catalyst was removed b filtration, and the filtrate was fractionally distilled under reduced pressure. After removal of water and n-butanol, 2-methyl-l,5-nentanediol was recovered as the fraction distilling bet een 80 C. and 89 C in an amount corresponding to 265 parts. Redistillation of the 2-methyl-1.5-pentanediol gave a heart out with the following properties: Boiling point, 89 C.: refra tive index 12 1.4532; specific gravity (20/4), 0.9724.

Example IV Eleven hundred forty parts of 2-(3.4-dihvdro- 1,2-pyranv1) methyl ether, 360 parts of water, and 1 part of glacial acetic acid were mixed in the reaction vessel that was employed in Exam le I. To the mixture was added 150 parts of Raney nickel hydrogenation catalyst. Air was displaced from the vessel by introduction of hydrogen, the vessel was closed from the atmos here and the hydrogen pressure was increased to 1500 pounds per square inch. The temperature of the vessel and its contents was raised to 150 C. and kept at this value for 4 hours. During this time the contents of the vessel were agitated. The vessel then was cooled and the pressure released, and the contents of the vessel were withdrawn. After removal of the hydrogenation catalyst by filtration, the mixture was fractionally distilled. 1,5-pentanedio1 was recovered in a conversion of 92% based on the amount of 2-(3,4-dihydro-1,2- pyranyl) methyl ether employed.

' Example V A mixture of 1140 parts of 2 -(3,4-dihydro- -1,2

pyranyl) methyl ether, 1100 parts water, and 200 parts Raney nickel hydrogenation catalyst was subjected according to the method of the pre-. ceding examples at 150 C. for 3 hours to the action of hydrogen gas under a pressure of 1500 pounds per square inch. After removal of the hydrogenation catalyst by filtration, the resultant mixture was fractionally distilled. pentanediol was recovered in a conversion of based on the amount of 2-(3,4-dihydro-1,2- I

consisting in hydrogenating at a temperature from about 50 C. to about 350 C. under a pressure of hydrogen from about 250 to about 10,000

pounds per square inch, in the presence of a hy-v drogenation catalyst, a mixture comprising 2- (3,4-dihydro-1,2-pyranyl) lower alkyl ether and water in an amount at least molecularly equivalent thereto. 7

3. The method of producing 1,5-pentanediol consisting in hydrogenating at a temperature from about 50 C. to about 350 C. under a pressure of hydrogen from about 250 to about 10,000 pounds per square inch, in the presence of a hydrogenation catalyst, a mixture comprising a 2- (Bfl-dihydro-Lil-pyranyl) organic ether wherein the dihydropyranyl group is unsubstituted and water in an amount at least molecularly equivalent thereto.

4. The method of producing 1,5-diols consisting in hydrogenating in the presence of a hydrogenation catalyst under conditions of an elevated temperature and a superatmospheric pressure of hydrogen conducive to hydrogenation reaction, a mixture comprising a 3,4-dihydro-L2-pyran having an organic substituent group attached to the carbon atom in position No. 2 of the dihydropyran ring by a hydrolyzable bond to a divalent atom of a non-metallic element of group VI of the periodic table of the elements, and water, and recovering a 1,5-diol from the mixture.

5. A method of preparing 1,5-pentanediol comprising subjecting 2-(3,4 dihydro 1,2-pyranyl) methyl ether to the simultaneous action of an aqueous acidic hydrolytic medium containing at least its molecular equivalent of Water, and of hydrogen under a pressure fromabout 250 to about 10,000 pounds per square inch, in the presence of a hydrogenation catalyst and at a.

temperature from about 50 C. to about 350 C.,

and recovering 1,5-pentanediol from the resultant mixture.

pounds per square inch in the presence of hydrogenation catalyst at a temperature from about 50 C. to about 350 C. and recovering tanediol from the resultant mixture.

7. A'method of preparing a 1,5-diol comprising subjecting in the presence of a hydrogenation catalyst a 3,4-dihydro-l,2-pyran having an organic substituent group attached to the carbon atom in position No. 2 of the dihydropyran ring by a hydrolyzable bond to a divalent atom of a non-metallic element of group VI of the periodic table of the elements, to the simultaneous action of an aqueous hydrolytic medium and hydrogen under conditions of an elevated temperature and a superatmospheric pressure of hydrogen eonducive to hydrogenation reaction, and recovering a 1,5-diol from the resultant mixture.

8. The method of producing 1,5-pentanediol consisting in subjecting to simultaneous hydrolysis and hydrogenation in the presence of a hydrogenation catalyst an unsubstituted 2-(3,4-dihydro-1,2-pyranyl) lower alkyl ether.

9. The method of producing 1,5-pentanediol consisting in subjecting to simultaneous hydrolysi and hydrogenation in the presence of a hydrogenation catalyst an otherwise unsubstituted derivative of 3,4-dihydro-L2-pyran having an organic substituent group attached to the carbon atom in position No. 2 of the dihydropyran ring by a hydrolyzable bond to a divalent atom of a non-metallic element of group VI of the periodic table of the elements.

10. The method of producing a 1,5-diol consisting in subjecting to simultaneous hydrolysis and hydrogenation in the presence of a hydrogenation catalyst a 3,4-dihydro-L2-pyran having an organic substituent group attached to the carbon atom in position No. 2 of the dihydropyran ring by a hydrolyzable bond to a divalent atom of a non-metallic element of group VI of the periodic table of the elements.

1 1. The method of producing Lfi-pentanediol from acrolein comprising the steps of condensing acrolein with a lower alkyl ether of vinyl alcohol by heating in admixture to produce a 2-(3,4-dihydro-1,2-pyranyl) lower alkyl ether, hydrogenating the products of the condensation reaction containing the 2-(3,4-dihydro-L2-pyranyl) lower alkyl ether by treatment with hydrogen gas in the presence of water and a hydrogenation catalyst, andrecovering 1,5-pentanediol from the products of the hydrogenation.

12. The method of producing a 1,5-diol from an alpha,beta-o1efinic aldehyde which comprises condensing the alpha,beta-olefinic aldehyde with a vinyl compound of the general formula wherein R denotes a hydrocarbon group to produce a 2-(3,4-dihydro-L2-pyranyl) ether having the group denoted by R linked to the ether oxygen atom, and subjecting said ether to the action of molecular hydrogen in the presence of a hydrogenation catalyst and water at an elevated temperature and under a superatmospheric pressure of hydrogen gas to produce a 1,5-diol.

CURTIS W. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,097,493 Leuck et a1 Nov. 2, 1937 2,440,929 Bremner et a1 May 4, 1948 OTHER REFERENCES Paul: Bulletin Soc. Chim. de France, 5th Se ries, vol. 1 part 2, (1934) pages 971-980. 

7. A METHOD OF PREPARING A 1,5-DIOL COMPRISING SUBJECTING IN THE PRESENCE OF A HYDROGENATION CATALYST A 3,4-DIHYDRO-1,2-PYRAN HAVING AN ORGANIC SUBSTITUENT GROUP ATTACHED TO THE CARBON ATOM IN POSITION NO.2 OF THE DIHYDROPYRAN RING BY A HYDROLYZABLE BOND TO A DIVALENT ATOM OF A NON-METALLIC ELEMENT OF GROUP VI OF THE PERIODIC TABLE OF THE ELEMENTS, TO THE SIMULTANEOUS ACTION OF AN AQUEOUS HYDROLYTIC MEDIUM AND HYDROGEN UNDER CONDITIONS OF AN ELEVATED TEMPERATURE AND A SUPERATMOSPHERIC PRESSURE OF HYDROGEN CONDUCIVE TO HYDROGENATION REACTION, AND RECOVERING A 1,5-DIOL FROM THE RESULTANT MIXTURE. 